NEW YORK (Reuters Health) - Women suddenly thrust into "surgical menopause" by hysterectomy don't have more severe mood symptoms than women going through gradual, natural menopause, a new study suggests.

Researchers who followed nearly 2,000 middle-aged women for 10 years found that those who had hysterectomies, with or without ovary removal, were as likely as women who went through natural menopause to experience depression or anxiety -- and for all women, those symptoms declined steadily within a few years.

"At least among women in midlife... mood symptoms don't seem to be a worry to take into consideration when making treatment decisions around hysterectomy and oophorectomy," said the study's lead author Carolyn Gibson, a researcher in the Department of Psychology at the University of Pittsburgh.

Although past studies have shown a link between hysterectomy and risk for depression, Gibson and her fellow researchers say it's still hard to tell whether the procedure is to blame.

Also unknown is whether the symptoms of surgically-induced menopause are any different from those of women who go through menopause naturally.

Gibson told Reuters Health the topic is important, because hysterectomies are very common.

About 600,000 women in the United States have their uterus removed during a hysterectomy every year, according to the U.S. Centers for Disease Control and Prevention.

The researchers say between 55 percent and 80 percent of women who undergo hysterectomy also have their ovaries removed -- a procedure known as oophorectomy.

Because a woman's ovaries generate estrogen, removing them induces menopause almost immediately.

Whether natural or induced, the change in a woman's hormone levels leading up to menopause, and in the years immediately afterward, often contributes to a range of symptoms, from anxiety and depression to insomnia and hot flashes.

To see whether a quick transition to menopause through surgery changes women's experience of the associated symptoms, Gibson's team turned to a database containing information on women's progression to, and through, the process.

They tracked about 2,000 women who were between 42 and 52 years old in 1996 and 1997, and were followed for more than ten years.

Over that period, 1,793 of the women went through menopause naturally, 76 had an elective hysterectomy and 101 had an elective hysterectomy and their ovaries removed.

All of the women were premenopausal at the beginning of the study and scored about the same on a scale that measures depression.

That scale goes from zero to 60 and, with higher scores representing more severe depression. A person with a score below 16 is not considered to be depressed.

For all three groups of women, depression scores decreased from the time they entered menopause to the end of the study period, and at about the same rates.

For those going through natural menopause, scores fell from 8.6 to 7.8. Those who had a hysterectomy saw their scores fall from 9.37 to 9.08, those who also had their ovaries removed went from 10.96 to 8.91.

Overall, the study shows depression symptoms in women who had a hysterectomy "declining in a very similar way as women who had a natural menopause," said Ellen Freeman, a research professor of obstetrics and gynecology at the University of Pennsylvania School of Medicine.

Freeman, who was not involved with the new study, told Reuters Health that it's important to know that the new study does not mean women will not be depressed after menopause -- just that the symptoms do decrease, and at about the same rate among women in each group.

Gibson and her colleagues write in the journal Obstetrics & Gynecology that this suggests symptoms of depression and anxiety improve as women enter their postmenopausal years.

The authors note, however, that the results may not be applicable to the general population, such as those with a history of mood disorders.